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javascript：入门笔记

2024-07-11 13:10:42   222人阅读

1：html注释：

<html><body><script type="text/javascript"><!--document.write("Hello World!");//两个正斜杠是 JavaScript 的注释符号，它会阻止 JavaScript 编译器对这一行的编译--></script></body></html>

2：支持三元运算符

greeting=(visitor=="PRES")?"Dear President ":"Dear ";

3：三种消息框

警告框：alert("text")

确认框：confirm("text")

提示框：prompt("noon",12)

 4：类似python的for in

var xvar mycars = new Array()mycars[0] = "Saab"mycars[1] = "Volvo"mycars[2] = "BMW"for (x in mycars){document.write(mycars[x] + "<br />")}

 5：异常处理

<html><body><script type="text/javascript">while(true){var x=prompt("Enter a number between 0 and 10:","")try{ if(x>10) throw "Err1"else if(x<0)throw "Err2"elsebreak} catch(er){if(er=="Err1") alert("Error! The value is too high")if(er == "Err2") alert("Error! The value is too low") }}</script></body></html

6：显示时间

<html><head><script type="text/javascript">function startTime(){var today=new Date()var h=today.getHours()var m=today.getMinutes()var s=today.getSeconds()// add a zero in front of numbers<10m=checkTime(m)s=checkTime(s)document.getElementById(‘txt‘).innerHTML=h+":"+m+":"+st=setTimeout(‘startTime()‘,500)}function checkTime(i){if (i<10)   {i="0" + i}  return i}</script></head><body onl oad="startTime()"><div id="txt"></div></body></html>

 

 


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